Patents
Grain refiners for aluminum castings generally contain titanium and boron in an aluminum base. Examples of these refiners may be found disclosed in U.S. Pat. Nos. 3,785,807, 3,857,705, 4,298,408 and 3,634,075. U.S. Pat. No. 3,676,111 discloses a method of refining aluminum base alloys by means of separate additions of boron and titanium. The invention teaches that (1) boron must be added to the aluminum base alloy, then (2) titanium is added with additional boron as may be required. Examples and suggestions of master alloy compositions for the titanium and boron additions in step (2) are limited to the well-known Al-3%B alloy and Al-5% Ti-1%B master alloys. The final cast alloy contains a Ti:B ratio between 1.4 and 2.2.